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| Re: Gridded MODIS lat/lon array [message #88186 is a reply to message #88177] |
Wed, 26 March 2014 18:44   |
dm_gty88
Messages: 8
Registered: October 2013
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Junior Member |
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On Wednesday, March 26, 2014 8:42:07 PM UTC+8, AMS wrote:
> Which specific 'MODIS gridded product' are you looking at? The various level 1, 2, and 3 MODIS products for atmospheres, oceans, and land have a variety of different gridding formats and conventions so the answer is likely to be (to an extent) dataset-specific.
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> Andy
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> On Wednesday, March 26, 2014 6:20:52 AM UTC-4, ddt88 wrote:
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>> hi,
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>> Is there a way I could do this: http://www.idlcoyote.com/map_tips/pixel_to_ll.html for a MODIS gridded product? I'm trying to avoid converting the images to geotiff so is it possible to do it for an HDF file? Thanks.
Hi Andy, I'm looking at surface reflectance (MOD09GQ), land surface temperature and vegetation indices. They're gridded to a sinusoidal projection.
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| Re: Gridded MODIS lat/lon array [message #88190 is a reply to message #88186] |
Thu, 27 March 2014 06:06 |
Andy Sayer
Messages: 127
Registered: February 2009
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Senior Member |
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Ah, sadly that's one of the MODIS products I don't have much experience with.
I found this older thread of yours on the group, did this not work? Or is it a different problem? https://groups.google.com/forum/#!topic/comp.lang.idl-pvwave /2EiVqFZn1So
On Wednesday, March 26, 2014 9:44:18 PM UTC-4, ddt88 wrote:
> On Wednesday, March 26, 2014 8:42:07 PM UTC+8, AMS wrote:
>
>> Which specific 'MODIS gridded product' are you looking at? The various level 1, 2, and 3 MODIS products for atmospheres, oceans, and land have a variety of different gridding formats and conventions so the answer is likely to be (to an extent) dataset-specific.
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>> Andy
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>> On Wednesday, March 26, 2014 6:20:52 AM UTC-4, ddt88 wrote:
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>>> hi,
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>>> Is there a way I could do this: http://www.idlcoyote.com/map_tips/pixel_to_ll.html for a MODIS gridded product? I'm trying to avoid converting the images to geotiff so is it possible to do it for an HDF file? Thanks.
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> Hi Andy, I'm looking at surface reflectance (MOD09GQ), land surface temperature and vegetation indices. They're gridded to a sinusoidal projection.
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| Re: Gridded MODIS lat/lon array [message #88191 is a reply to message #88187] |
Thu, 27 March 2014 06:13 |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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ddt88 writes:
> Hello David, I'm working with a large number of files so I want to avoid having to convert each hdf to geotiff for processing efficiency. I'm quite confused with the geotiff info and can't understand how I could extract the same information from the metadata of HDF files.
The information to navigate the image is in the metadata of the HDF
file. You are given the projection information (Sinusodial with
spherical datum) and the projected XY meter locations of the upper left
point and the lower right point of the image. Then, you are told the
dimensions of the image (4800x4800 in my case). This is everything you
need to know to navigate the image. For example, for the MOD09GQ image I
have here, I set the map coordinate object up like this:
IDL> map =cgmap('sinusoidal', ellipsoid=9, $
xrange=[6671703.118000d, 7783653.637667d], $
yrange=[3335851.559000d, 4447802.078667d], $
position=[0,0,1,1])
IDL> cgDisplay, 800, 800
IDL> cgImage, image, Stretch=2
IDL> cgMap_Grid, /Label, /cgGrid, Color='goldenrod', Map=map
I'm not sure why you think you need to make a GeoTiff file out of it for
"processing efficiency".
I read the information out of the file with NCDF_Browser. But, I'm sure
it is possible to read the metadata out of the file directly, too.
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
Sepore ma de ni thue. ("Perhaps thou speakest truth.")
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